Mazda's 2.6 was also NA, but classed as a 7.8L NA. The reason Mazda had to use the variable length intake was because of that classing. In order to get their power output up to competitive levels they had to achieve unheard of volumetric efficiencies, and without forced induction. The only way to get enough air into the engine at full scream was to cut huge intake holes into the side of the block. But at lower revs these ports would stall.
So the runners would extend at pit speeds to allow the inertia of the air flow to keep the ports from stalling, but in the higher RPM range the long runners would become a restriction so they would pull back.
Classed as a 7.8L Mazda needed to be making nearly 800 HP to be competitive. They got 750 out of this little 2.6L naturally aspirated block.
Long live the 787B!
http://www.youtube.com/watch?v=9675TKafw3ghttp://www.youtube.com/watch?v=K1BWv7iPFUgEDIT, PS: I'm a total rotor head, and have owned four different RX-7s, but am down to two now. One coupe, and one convertible. The convertible is getting a new engine installed (this is a more expensive project than my home theater), but I have the
block.
